The present invention relates to generation of a measurement program used in NC machining and machining management carried out using the measurement program. More specifically, in NC machining carrying out a variety of machining control using numerical control information, the present invention relates to an improved method and device for generating a measurement program from an NC program used in actual machining, and also for machining management based on a measurement result obtained by executing the generated measurement program.
In the present invention, a measurement program as described above is generated at any time regardless of whether or not an NC program is on a run. The measurement program has generality so that it can be used at any time not only for machining which is being carried out but also for machining using another machine tool. When an NC program is modified, the measurement program can also be modified based on the modified program.
A numerically controlled machine tool can automatically control an operation of a machine tool by inputting an NC program. Recently, a numerically controlled machine tool has been in wide use in a variety of industrial fields as a computer numerical control machine tool (CNC machine tool) with a combination of techniques such as microprocessor techniques, power electronics techniques, and software techniques.
Usually, individual information such as a tool index command, a main spindle rotation command, a feeding rate command, axis movement/interpolation command, and an auxiliary function command, together with machining history, is incorporated in numerical control information such as an NC program or the like. Numerical control information appropriate for a machine tool to be controlled is thus generated as an NC program.
An NC program generated as described above is used for a variety of machining. However, for high quality machining, measurement necessary for machining is carried out on a final machining product or during each machining process. Based on the measurement result, machining control compensation is carried out at a subsequent machining process on a workpiece to be used next or on the workpiece measured. In conventional and primitive measurement, size of parts is measured partially using a simple measurement instrument such as a micrometer or slide calipers, according to a process inspection table. At a final inspection stage, all important portions of parts are measured. If there is a problem in the measurement result, it is fed back to NC machining. Reflection of the measurement result on the machining control has conventionally been carried out by skilled workers with considerable experience through oral communication or memorandum between operators. No real time and automatic reflection of the measurement result has been possible.
Furthermore, only limited measurement has been possible using a conventional simple inspection process. Therefore, accurate measurement has been dependent on the final inspection, which leads to a delay in realizing the existence of a problem and lower yield by NC machining.
To solve the problems described above, an automatic programming method for measurement has been proposed for reflecting a measurement result on NC machining after sequential automatic measurement using a three dimensional coordinate measurement machine during the NC machining with a measurement program previously generated in each machining process or in a final machining process. According to this conventional technique, regarding measurement itself, it has been possible to perform predetermined measurement quickly and accurately without a skilled operator.
However, the conventional automatic programming is carried out by CAD and CAM, through complex processes using material data, final workpiece form data, tool data, and the like. Therefore, the conventional automatic programming can not be used in all NC machining, and it requires a large-scale machine. Moreover, it is rarely usable except for a case where large number of products are machined using one and the same NC program.
Moreover, a measurement program by the automatic programming is generated based on final product form data, especially on a working, drawing. Therefore, no measurement program optimal for a workpiece form in an operation element, in a machining element or during a machining process in an arbitrary step during an actual execution of the NC program is provided.
The machining element here means a group of operation elements at one machining position of a workpiece. In other words, an operation element means single machining carried out by a tool. For example, it means a single operation such as boring and milling. A machining element means to finish machining through a combination of operation elements on one machining position of a workpiece. For example, in a case of threaded hole drilling, a machining element is defined as a combination of center hole drilling, prepared hole, and tapping. In the present specification, a machining process means a series of all machining operations carried out without a posture change of a workpiece fixed on a machine tool.
In a recent NC machining trend, NC programs to be used are as open and flexible as they can possible be. During actual machining, programs are often modified for the sake of an optimal machining method. Each program is made as a module or having more generality so that unrestricted changes in the program are possible. As a result, a conventional machining program determined rigidly by a working drawing can not adapt with each step in a machining process, actual operation elements or machining elements, and therefore can not be made applicable to a recent state of the art NC machine tool.
Moreover, recent state of the art NC machining carries out CIM (Computer Integrated Manufacturing) using not only a single machine tool but also a combination of other machine tools. In such a case, a conventional, fixed measurement program can neither be applied to other machine tools nor learn in order to be applicable to other machine tools.
The present invention is created taking the conventional problems described above into consideration. The object is to generate a measurement program through analysis of an actual machining program, not based on working drawings. It also aims to provide a new method for machining process control reflecting a measurement result obtained by the measurement program on NC machining.
To achieve the objects described above, the present invention analyzes an NC program, extracts a workpiece form at each step of an actual machining process provided in the NC program as a geometric model, and generates a measurement program based on the geometric model.
When such a measurement program is running, a real time measurement result can be obtained during machining so that the result can immediately be reflected on the subsequent machining process. A modified machining program can thus be used immediately.
Furthermore, according to the present invention, if a machining program is modified, a measurement program is also modified in accordance with the new machining program. It is advantageous that an NC program and a measurement program can always be related to each other and run during actual machining or prior to the subsequent machining step. In NC machining wherein machining control is carried out by an NC program, one aspect of the present invention comprises a workpiece form information extracting unit for extracting information regarding a workpiece form in an arbitrary step of each operation element machining, machining element machining, or machining process machining, through analysis of the NC program, a geometric model generating unit for generating a geometric model of in an arbitrary step based on the workpiece form information, and a measurement program generating unit for generating a measurement program based on the geometric model.
In an NC machining process wherein machining control is carried out by an NC program, another aspect of the present invention comprises a dividing unit for dividing the NC program in each operation element machining or machining element machining by analyzing the NC program, a machining element extracting and coordinate system transforming unit for extracting workpiece form information at each operation element machining or machining element machining divided by the dividing unit, a geometric model generating unit for generating a geometric model in three dimensional coordinate system based on the workpiece form information, a measurement path generating unit for determining a measurement path based on the geometric model, and a measurement program generating unit for generating a measurement program based on the measurement path.
According to still another aspect of the present invention, a machining controller for carrying out the measurement program described in claim 1 further comprises a measurement result analyzing means for using a measurement result as machining control information, the measurement result being obtained by carrying out the measurement program at the end of at least one process among processes defined in the NC program.
In an NC machining wherein machining control is carried out by an NC program, yet another aspect of the present invention comprises the steps of workpiece form information extraction for extracting information regarding a workpiece form in an arbitrary step of each operation element machining, machining element machining, or machining process machining through analysis of the NC program, geometric model generation for generating a geometric model of a workpiece in an arbitrary step based on the workpiece form information, and measurement program generation for generating a measurement program based on the geometric model.
In an NC program wherein machining control is carried out by an NC program, a still further aspect of the present invention comprises the steps of division of the NC program in each operation element machining or machining element machining by analyzing the NC program, machining element extraction and coordinate system transformation for extracting workpiece form information at each operation element machining or machining element machining divided in the above step, geometric model generation for generating a geometric model in a three dimensional coordinate system based on the workpiece form information, measurement path generation for determining a measurement path based on the geometric model, and measurement program generation for generating a measurement program based on the measurement path.
According to a still further aspect of the present invention, a machining control method for carrying out the measurement program described in claim 4 uses a measurement result as machining control information, the measurement result being obtained by carrying out the measurement program at the end of at least one process among processes defined in the NC program.
In the machining control method described in claim 6, the present invention generates a form model in the process based on a measurement result and provides the model as machining control information for a subsequent machining process.
In the method described in either claim 6 or claim 7, the present invention provides tolerance data to the measurement program.
The present invention is also a medium for storing a program which stores the procedures of workpiece form information extraction for extracting information regarding a workpiece form in an arbitrary step of operation element machining, machining element machining, or machining process machining through analysis of the NC program, geometric model generation for generating a geometric model of a workpiece in an arbitrary step based on the workpiece form information, and measurement program generation for generating a measurement program based on the geometric model.
Furthermore, the present invention is also a medium for storing a program to carry out procedures using the measurement result obtained by the measurement program described in claim 4 as a machining control method.